1. Field of the Invention
This invention relates to brushless motors and, more particularly, to a novel and highly-effective brushless motor including means for detecting the angular position of the rotor thereof.
2. Description of the Prior Art
In the case of conventional brushless motors, when it is desired to provide for obtaining information about the angular position of the rotor, a sensor such as a Hall element is widely used.
Japanese patent publication No. 31304/1984, published Aug. 1, 1984, describes another method of obtaining such information, wherein an RF current flows through an excitation coil to detect a change in an induction current due to a change in position of the excitation coil relative to a stator coil.
Conventional motors of the first type described above cannot be made as compact as is desired in many applications, since the sensor element and its lead wires require a substantial amount of space. The sensor element and lead wires also add significantly to the cost of the motor.
In conventional motors of the second type described above, the sensor element can be omitted. However, an excitation coil is required, together with an inductor for increasing the induction current between the excitation coil and the stator coil. Moreover, a balancer for the inductor must be mounted in the rotor. As a result, the overall structure becomes larger, more complex, and more expensive than is desired in many applications.